Recent advance in information communication (IT) technologies leads to development of various wireless communication technologies. Among others, WLAN is a technology that is based on a wireless frequency technology and that allows for wirelessly accessing the Internet in a home or a specific service providing area by using portable terminals such as personal digital assistants (PDAs), laptop computers, and portable multimedia players (PMPs).
To overcome a weakness of WLAN, i.e., limited communication speed, the IEEE 802.11n standard has been recently established. This standard targets increasing network speed and reliability as well as expanding the operation range of the wireless network. Specifically, the IEEE 802.11n supports a high throughput (HT) in which data processing speed reaches up to 540 Mbps and is based on the MIMO (Multiple Inputs and Multiple Outputs) technology in which a multi-antenna is used in each of the transmit unit and the receive unit so as to optimize data rate while minimizing transmission errors.
As WLAN is spreading over and over and various applications using this are developed, demand for new WLAN systems, which may support a higher data processing rate than that supported by IEEE 802.11n, is growing up. The next-generation WLAN system supporting very high throughput (VHT) is a subsequent version of 802.11n WLAN and is one of new IEEE 802.11 WLAN systems as recently suggested to support a data processing rate of 1 Gbps or more in the MAC service access point (SAP).
A next-generation WLAN system backs up MU-MIMO (Multi User Multiple Input Multiple Output)-based transmission in which a plurality of STAs attempts to simultaneously access the channel in order to efficiently use wireless channels. In such MU-MIMO transmission scheme, an AP may transmit packets to one or more MIMO-paired STAs at the same time.
As various communication services such as smart grid, e-Health, and Ubiquitous are introduced, M2M (Machine to Machine) technologies gain popularity to support the services. A sensor for sensing temperature or moist, a camera, a home appliance such as TVs, a processing machine used in the factory, or vehicles or other large-scale machines may be an element constituting an M2M system. The elements constituting an M2M system may attend data transmission and receipt based on WLAN communication.
An M2M supportive WLAN system may be specified to use a frequency band other than the existing frequency band used for data transmission and receipt. In contrast to a conventional system using a band of 5 GHz, a WLAN system supporting M2M may be set to use a band of 900 MHz.
As configuring an M2M supportive WLAN system, a wireless apparatus uses a frequency band not to overlap the frequency band supported by the existing WLAN system, and thus, may generate and transmit a data frame, i.e., PPDU (PLCP (Physical Layer Convergence Procedure) Protocol Data Unit), without considering backward compatibility. In other words, it is not required to support compatibility with legacy stations (STAs) that operate in the existing WLAN system. Accordingly, when control information for legacy STAs is, upon transmission, included in PPDU in accordance with the existing PPDU transmission/reception scheme, overhead may occur unnecessarily. Therefore, there is a need for an improved PPDU transmission and reception method that may support efficient data exchange in an M2M supportive WLAN system.